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The magnitude Mw = 8.0 earthquake that struck China's Sichuan region on 12 May 2008 has been imaged by X, C, and L-band SAR satellites (ASI's Cosmo-Skymed, ESA's ENVISAT, and NASDA's ALOS, respectively), allowing to attempt the recovering of the ground deformation associated to the fault dislocation. We analyzed all the available Cosmo stripmap images (3-m resolution), some ENVISAT frames, and more than sixty ALOS-PALSAR scenes. The X and C band interferograms show good coherence only in the lowland, near the city of Chengdu, but the coherence decreases dramatically in the strong relief areas. Moreover their spatial coverage is limited with respect to the large extent of the fault (~ 300 km long). The best coverage is provided by PALSAR interferograms which maintain very good coherence also in the mountain areas, thanks to the long wavelength of the L band (23.8 cm). We calculated ~ 45 differential PALSAR interferograms across time spans of a few months, obtaining a good view of the co-seismic surface deformation along the fault. We observe over 2.5 m of Line of Sight ground displacement. We use the displacement field to infer the geometry and the slip distribution of the seismogenic fault, by means of a linear and non-linear inversion of an analytic elastic source; an additional modelling is then performed by means of a finite element approach.

The Volcán de Colima (CV) is currently the most active Mexican volcano. After the 1913 plinian activity the volcano presented several eruptive phases that lasted few years, but since 1991 its activity became more persistent with vulcanian eruptions, lava and dome extrusions. During the last 15 years the volcano suffered several eruptive episodes as in 1991, 1994, 1998-1999, 2001-2003, 2004 and 2005 with the emplacement of pyroclastic flows. During rain seasons lahars are frequent affecting several infrastructures such as bridges and electric towers. This work is focused on the detection of surface deformation with centimetre or sub-centimeter accuracy of the Volcán de Colima and surrounding areas. We try to assess the amount and the spatial extension of surface movements of the CV and to get insights into the causes of the surface deformation by using Interferometric Synthetic Aperture Radar (InSAR), a powerful tool ensuring measurements at high-accuracy over large areas. The image dataset acquired by ESA ENVISAT ASAR (C band) and ALOS PALSAR (L Band) sensors, has been processed using Advanced interferometric techniques (A-InSAR) to overcome the really challenging sources of decorrelation related to the setting context, mainly vegetation and atmosphere, in order to give us the opportunity to detect also very low rates of deformations. The main objectives of the interferometric analysis is the measurement of deformations in the CV in relation with active tectonics and gravity induced spreading, the identification of magma migration below the surface in the last decade, the detection of the incipient movements of volcanic landslides and large scale volcano instability, and the kinematics of the Colima rift. We present preliminary results of the A-InSAR processing, in the framework of the interdisciplinary Colima Deformation project (ColDef).

We investigated the surface effects of the April 6th, 2009, L’Aquila earthquake (Mw 6.3). The earthquake affected a large area in Central Italy causing strong damage to cities and villages in the epicentral region. The main goal of this work is the detection and characterization of the geological effects, such as Deep-seated Gravitational Slope Deformation (DGSD), which are gravity-driven ground movements occurring on large (1-5 km length, 100-500 m depth and width) rock volumes. To this aim we exploited the capabilities of the new High Resolution COSMO-SkyMed SAR2000 instrument, using the Differential SAR Interferometry (DInSAR) technique. We used a right ascending, Stripmap mode (35° incidence angle), coseimic image pair (April 4 - April 12) to measure the surface displacement. . We removed the topographic phase contribution using a detailed DEM at 5-m resolution . Local areas showing fringe complexities not directly attributed to the main tectonic pattern have been detected. By means of a geomorphological and geological analysis we interpreted such fringe patterns as due to ground displacement occurred along two different DGSD, one close to Roio Piano village, and the other North of the Barisciano village. The first DGSD is a sackung induced by the particular structural setting (down dip strata) and the high relief energy, whilst the second one appears to be a lateral spread of carbonatic bedrock. We unwrapped the interferogram to measure the local movements, and found 4-5 cm of LOS (Line Of Sight) displacement in both areas. The DGSD movement was triggered by the earthquake ground shaking, and, although in this case it did not result in a catastrophic collapse of the rock masses, it certainly indicates the presence of an increased ground shaking hazard in these areas. The L’Aquila earthquake is the second case study where the seismic triggering of DGSD has been recognized by DInSAR. It is worth noting that a step forward in terms of scale detail has been achieved thanks to the COSMO-SkyMed spatial resolution and frequency band.

The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement. Extensive 1:10,000-scale geological and geomorphological mapping has been carried out, focusing on the characterization of the long-term expression of the Paganica Fault at the surface. The field mapping was integrated by observations, made on 1:33,000 scale aerial photographs (GAI), 5-m-resolution Digital Elevation Model and standard morphometric derivatives (hill-shaded and slope angle maps, Spatial Analyst™). Particular attention was devoted to the study of the continental deposits and landforms affected by cumulative offset with the aim to reconstruct the Quaternary deformational history of the fault. The fault runs for a total length of 20 km and, along with antithetic faults on its hanging-wall, forms the graben of the Middle Aterno River Valley. The whole fault system and the variable setting of deformation affecting the continental deposits at the surface were identified. The Paganica long-term morphologic signature is represented by a set of prominent scarps formed by the tectonic juxtaposition of late Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by lower scarps in late Pleistocene-Holocene deposits. In addition, evident Quaternary erosional and depositional paleosurfaces were recognized and sampled for 14C and OSL (Optically Stimulated Luminescence) and tephra chronology dating for long-term slip-rate calculations. This study resulted helpful to locate four paleoseismological investigations (see Pantosti et al. talk) and to provide the appropriate context for correctly interpret the depositional bodies outcropping on the trench walls. These paleoseismological investigations evidenced the presence of repeated late Pleistocene-Holocene activity and allowed for slip-rate estimation at a shorter time-scale. Such estimates were valuable for a comparison with the preliminary estimates on late Pleistocene calculations carried out by geomorphological investigations. Moreover, we correlated co-seismic deformations with the long-term morphologies and structures. The 2009 co-seismic ruptures show a general coherence with the long-term Paganica fault trace, both in terms of location and style. However, the limited extent of the 2009 surface ruptures coincides with the portion of the fault trace where deformation is more localized and few splays contribute to the extension. This is also testified by the presence on its hanging-wall of a large late Pleistocene-Holocene alluvial fan that subsides over the basin depocenter. Conversely, where the Paganica fault system branches out, various splays accommodated the small 2009 co-seismic throw, resulting in a distributed and not evident extensional strain. The preserved fault-related geomorphology is evidence for the persistence of the rupture complexities during Quaternary. On this light, further studies on the style of fault activity are needed to estimate if the Paganica fault is capable of earthquakes with Magnitude larger than the 2009 event.